1. Field of the Invention
The present invention relates to a recording medium suitable for use in recording using water-based inks, ink-jet recording method and a dispersion. In particular, this invention relates to a recording medium which can provide images high in optical density, bright in color tone and high in resolution, and has excellent ink-absorbing capacity, an ink-jet recording method using such a recording medium, and a dispersion of an alumina hydrate, which is suitable for use in production of the recording medium.
2. Related Background Art
In recent years, an ink-jet recording system, in which minute droplets of an ink are flown by any of various working principles to apply them to a recording medium such as paper, thereby conducting recording of images, characters and/or the like, has been quickly spread as a recording apparatus for various images in various applications including information instruments because it has features that recording can be conducted at high speed and with a low noise, color images can be formed with ease, recording patterns are very flexible, and development and fixing processes are unnecessary. Further, it begins to be applied to a field of recording of full-color images because images formed by a multi-color ink-jet recording system are comparable in quality with multi-color prints by a plate making system and photoprints by a color photographic system, and such records can be obtained at lower cost than the usual multi-color prints and photoprints when the number of copies is small. With the improvement in recordability, such as speeding up and high definition of recording, and multi-coloring of images, recording apparatus and recording methods have been improved, and recording media have also been required to have higher properties.
In order to satisfy such requirements, a wide variety of recording media have been proposed. For example, Japanese Patent Application Laid-Open No. 52-53012 discloses paper for ink-jet, in which a base paper web low in sizing degree is impregnated with a surface coating. Japanese Patent Application Laid-Open No. 53-49113 discloses paper for ink-jet, in which a sheet containing urea-formalin resin powder therein is impregnated with a water-soluble polymer. Japanese Patent Application Laid-Open No. 55-5830 discloses paper for ink-jet recording, in which a coating layer having good ink absorptiveness is provided on a surface of a base. Japanese Patent Application Laid-Open No. 55-51583 discloses that amorphous silica is used as a pigment in a coating layer. Japanese Patent Application Laid-Open No. 55-146786 discloses that a coating layer formed of a water-soluble polymer is used.
In U.S. Pat. Nos. 4,879,166 and 5,104,730, and Japanese Patent Application Laid-Open Nos. 2-276670, 4-37576 and 5-32037, there have been proposed recording sheets having a layer using an alumina hydrate of a pseudoboehmite structure.
As described in U.S. Pat. Nos. 4,374,804 and 5,104,730, and Japanese Patent Application Laid-Open Nos. 58-110287 and 4-37576, it has also been conducted to form an ink-receiving layer of a multi-layer structure using a silica or alumina material.
However, the conventional recording media have involved the following problems:
1) U.S. Pat. No. 5,104,730, and Japanese Patent Application Laid-Open Nos. 2-276670, 2-276671 and 3-275378 disclose recording media having extremely narrow distribution of pore radius. As disclosed in Japanese Patent Application Laid-Open Nos. 4-267180 and 5-16517, however, individual dyes for inks (cyan, magenta, yellow and black) and solvents for the inks are selectively adsorbed in pores of a specific size. Therefore, bleeding may occur on prints if the composition of ink is changed.
The bleeding refers to a phenomenon that edges of boundaries of multi-color printed areas can not be resolved because of feathering caused when ink is still fluid before it is fixed in the ink-receiving layer.
2) U.S. Pat. No. 5,104,730, and Japanese Patent Application Laid-Open Nos. 2-276670, 2-276671 and 3-275378 disclose recording media having pore radius distribution as narrow as 10 to 30 xc3x85 in average pore radius. In this pore radius distribution, dye adsorptiveness is good, while the absorptiveness of solvent is insufficient, resulting in the occurrence of beading.
The beading mentioned in the present invention refers to a phenomenon in which dots irregularly move in the plane direction of the surface of an ink-receiving layer when ink is still fluid before it is fixed in the ink-receiving layer, thus forming new aggregates together with adjacent dots to cause an unevenness in the density of recorded images.
3) In printing of color images, inks increase in quantity. The inks printed cannot be completely absorbed in pores, but run out on the surface of an ink-receiving layer, so that bleeding occurs, resulting in deterioration in print quality.
4) High-speed printing requires to have good drying ability. However, absorbing rate is insufficient, and the printed surface is hence not dry when discharged out of a printing apparatus, so that output images may be possibly impaired by contact.
5) There is a problem that the solids concentration of a dispersion of a pigment or the like cannot be increased because the viscosity of the dispersion increases with time, resulting in a failure to apply it. As a measure for the solution of the problem, Japanese Patent Application Laid-Open No. 4-67986 discloses a process in which the polymerization degree of a polymer as a binder is lowered. However, this process involves problems of defective appearance such as cracking in an ink-receiving layer, reduction in water fastness, and the like, and hence still requires a further improvement.
6) There is a problem that since the viscosity of the dispersion is high, its solids concentration cannot be increased. As a measure for the solution of the problem, Japanese Patent Application Laid-Open No. 4-67985 discloses a process in which an acid such as a monocarboxylic acid is added as a dispersant. However, this process is accompanied by productive problems that offensive odor is given, and corrosion is caused.
7) In order to improve ink absorptiveness and resolution of images, U.S. Pat. Nos. 4,780,356, 4,374,804 and 5,104,730, Japanese Patent Publication No. 3-72460, and Japanese Patent Application Laid-Open Nos. 55-11829, 58-110287, 62-270378 and 4-37576 disclose a process in which an ink-receiving layer of a two or more multi-layer structure is formed. However, the process involves a problem that coating and drying must be conducted at least twice for forming the ink-receiving layer, and so the number of processes increases. In addition, since the physical property values of the individual layers are different from each other, there are also problems of changes with time, defective appearance such as cracking in the ink-receiving layer, and separation and peeling of the layers from each other upon printing or the like.
8) Japanese Patent Application Laid-Open No. 3-281384 discloses an alumina hydrate forming an aggregate like a needle, which is in the form of a column having an aspect ratio of not higher than 3 and unidirectionally oriented, and a process for forming an ink-receiving layer using the alumina hydrate. However, since particles of the alumina hydrate are oriented and compacted, spaces among the alumina hydrate particles in the ink-receiving layer tend to narrow. Therefore, the pore radius is partial to a narrow side, and distribution of pore radius has a tendency to narrow. As a result, there is a problem that beading occurs as described above.
The present invention has thus been made with a view toward solving the above problems and has as its object the provision of a recording medium which can be suited to inks of various compositions, is excellent in ink absorptiveness, can suppress feathering or bleeding of print and occurrence of beading and can provide images high in optical density, and an ink-jet recording method using this recording medium.
Another object of the present invention is to provide a recording medium which can effectively adsorb or absorb a dye and a solvent, which are components for an ink, and hence permits good coloring and quick drying, and an ink-jet recording method using this recording medium.
A further object of the present invention is to provide a dispersion of a pigment, which is suitable for use in production of the above recording media.
A still further object of the present invention is to provide a recording medium in which both dispersibility of a dispersion for coating and dye-adsorbing ability are satisfied, an ink-jet recording method using the recording medium, and a dispersion suitable for use in production of the recording medium.
The above objects can be achieved by the present invention described below.
According to the present invention, there is thus provided a recording medium comprising an alumina hydrate having an average pore radius of 20 to 200 xc3x85 and a half breadth of pore radius distribution of 20 to 150 xc3x85.
According to the present invention, there is also provided a recording medium comprising a base material and an ink-receiving layer which comprises a pigment and a binder and is provided on the base material, wherein the pigment is an alumina hydrate and the ink-receiving layer has an average pore radius of 20 to 200 xc3x85 and a half breadth of pore radius distribution of 20 to 150 xc3x85.
According to the present invention, there is further provided a recording medium comprising principally pulp fibers and a filler, wherein the filler comprises an alumina hydrate having an average pore radius of 20 to 200 xc3x85 and a half breadth of pore radius distribution of 20 to 150 xc3x85.
According to the present invention, there is still further provided a recording medium comprising an alumina hydrate having at least two peaks in pore radius distribution.
According to the present invention, there is yet still further provided a recording medium comprising a base material and an ink-receiving layer which comprises a pigment and a binder and is provided on the base material, wherein the pigment comprises an alumina hydrate and the ink-receiving layer has at least two peaks in pore radius distribution.
According to the present invention, there is still further provided a recording medium comprising principally pulp fibers and a filler, wherein the filler comprises an alumina hydrate having at least two peaks in pore radius distribution.
According to the present invention, there is yet still further provided a recording medium comprising an alumina hydrate containing 0.01 to 1.00% by weight of titanium dioxide.
According to the present invention, there is yet still further provided a recording medium comprising a base material and an ink-receiving layer which comprises an alumina hydrate containing 0.01 to 1.00% by weight of titanium dioxide and is provided on the base material.
According to the present invention, there is still further provided a recording medium comprising principally pulp fibers and a filler, wherein the filler comprises an alumina hydrate containing 0.01 to 1.00% by weight of titanium dioxide.
According to the present invention, there is yet still further provided an ink-jet recording method comprising ejecting minute droplets of an ink from an orifice to apply the droplets to a recording medium, thereby conducting printing, wherein one of the recording media described above is used as the recording medium.
According to the present invention, there is yet still further provided a dispersion of an alumina hydrate, which is obtained by dispersing an alumina hydrate containing 0.1 to 1.0% by weight of a nitrate anion and having an average pore radius of 20 to 200 xc3x85 and a half breadth of pore radius distribution of 20 to 150 xc3x85 in deionized water, wherein the dispersion having a solids concentration of 15% by weight has a viscosity of not higher than 75 cP as measured at 20xc2x0 C. and a shear rate of 7.9 secxe2x88x921.
According to the present invention, there is yet still further provided a dispersion of an alumina hydrate, which is obtained by dispersing an alumina hydrate containing 0.1 to 1.0% by weight of a nitrate anion and having at least two peaks in pore radius distribution in deionized water, wherein the dispersion having a solids concentration of 15% by weight has a viscosity of not higher than 75 cP as measured at 20xc2x0 C. and a shear rate of 7.9 secxe2x88x921.
According to the present invention, there is yet still further provided a dispersion of an alumina hydrate, which is obtained by dispersing a titanium dioxide-containing alumina hydrate containing 0.1 to 1.0% by weight of a nitrate anion in deionized water, wherein the dispersion having a solids concentration of 15% by weight has a viscosity of not higher than 75 cP as measured at 20xc2x0 C. and a shear rate of 7.9 secxe2x88x921.